During a dialysis treatment a filter with a semi-permeable membrane is used to remove substances from the patient and control the patient weight. This semi-permeable membrane is dividing the dialysate side and the blood side. Blood cells are not able to pass such a semi-permeable membrane as long as there are no ruptures of the fibers.
In case of a membrane rupture it is possible that not only plasma but also blood cells are passing the membrane to the dialysate side. This is dangerous for the patient and so a standard measure to detect such ruptures is to position an optical sensor (blood leak detector) at the outlet of the dialysis fluid/ultrafiltration fluid in order to detect blood diluted inside the line as early as possible and provide alarm to staff for evaluation.
State of the art blood leak detectors measure the absorbance of different light spectra in the visible range. Intrusion of environmental light in same range can impact and affect the measurement method and cause false alarms.
Known approaches to these problems combine a tube and sensor fixed inside a dialysis device, employ a sensor having a cover door on the sensor itself which need to be open and closed for tube loading, or use high sided arrangements in order to reduce a total impact caused by foreign light.
The aforementioned issue is largely irrelevant for integrated sensors inside dialysis devices where it is not part of the disposable set but integrated in the device fluid path. If, however, a sensor is mounted on a surface outside the housing environmental light has a relevant impact. Approaches like inserting tubing and opening/closing a cover door to protect against environmental light have the severe disadvantage that manual steps are required, and that an automatic insertion of multiple tubing at a same time and a usage of such cover is not possible. Besides, a tube fixedly integrated into the sensor is does not allow for the usage of a disposable set as an exchangeable part.
In a pre-assembled disposable kit, where ail the bloodline and the filters are fixed on a holder, the holder has the aim and purpose to facilitate and speed up the setup of the kit on the machine. This is key important for the user to improve usability and speed while avoiding mistakes. Therefore, some tube portion of the kit must fit directly into the machine sensor during the loading of the kit, for instance the BLD (Blood Leak detector), without any additional cover.